Bait condition and bait size play a part in bait sink rate. The faster bait sinks, the less available it is to predatory seabirds during line setting. Bait condition also plays a part in the ease of hooking ('baiting') and whether the bait will stay on the hook (quality).
Bait Life Status
Live bait sinks more slowly than dead bait; using it increases the likelihood seabirds will be caught. Recent research recommends the use of dead bait only.
Bait Thaw Status
In fisheries where lead weights are added to branch lines, as long as bait (fish, squid) are thawed to an extent that permits hooks to be inserted without undue force, bait thaw status has no effect on sink rates. In fisheries where leaded swivels are not added to branch lines, the use of unthawed bait slows sink rates. However, the difference is minor and less important than other factors that affect gear sink rates.
Bait Size (and species)
Small species of fish bait should be used in preference to squid bait. This is because larger squid bait sinks considerably more slowly than small fish bait. Common fish baits are pilchards, sardines and various species of mackerel (Japanese, blue, yellow-tail). The difference in sink rates between large and small fish baits of the same species is minor. Bait species affects the probability of catching different bycatch species (see the description for 'Fish not squid bait'.
Bait hooking position is important. To ensure fast sink rates, baits should be hooked in either the head (fish) or tail (fish and squid), not in the middle of the back or top of the mantle (squid).
- ACAP. 2011. AC5 Annex 7: Summary advice statement for reducing impact of pelagic longline gear on seabirds. Seabird Bycatch Working Group. Fourth Meeting of the Seabird Bycatch Working Group, Guayaquil, Ecuador.